1. Field of the Invention
The present invention relates to a shell lock seaming machine, and more specifically, to a shell lock seaming machine for winding a sheet member around the outer periphery of a shell case.
2. Description of the Related Art
Conventionally, there have been used shell lock seaming machines which employ a so-called over-winding method by which a sheet member is wound around the outer periphery of a shell case used as a silencer to reduce the noise created by an internal combustion engine in order to enhance the noise insulating properties of the silencer and make the silencer look more attractive.
The over-winding method will be schematically described with reference to FIG. 11A to FIG. 11F. First, a metal sheet member 100 shown in FIG. 11A is wound to a cylindrical shape as shown in FIG. 11B and both the ends thereof are coupled with each other by a lock seam 101; flanges 103, as shown in FIG. 11, are formed to both the opening edges of the shell case 102; contents 104 composed of barrier plates, end plates and the like to which an inner pipe is fixed are inserted from one of the opening edges as shown in FIG. 11D; thereafter, a sheet member 105 is fed below the shell case 102 and bent along the lower half of the shell case 102 by moving a pair of presser plates 106 upward as well as both the ends of the sheet member 105 are raised as shown in FIG. 11E; and then both the ends of the sheet member 105 are coupled with each other by a lock seam 107 as shown in FIG. 11F to thereby form a double-walled shell case.
At the above step at which the sheet member 105 is wound around the outer periphery of the shell case 102, there has been conventionally employed, as shown in FIG. 12A and FIG. 12B, a mechanism for supporting the shell case 102 which is arranged such that a pair of mandrels 108, 109 are disposed in confrontation with each other, the shell case 102 is located between the mandrels 108, 109 by a robot or the like as shown in FIG. 12A, thereafter both the mandrels 108, 109 are inserted into the shell case 102 from both the opening edges thereof to thereby support the shell case 102 as shown in FIG. 12B (for example, JP-A-06-269884).
The outer peripheral shape of the conventional mandrels 108, 109 is exclusive to the shape of both the opening edges of the shell case 102 to be processed. Thus, when a shell case having a different opening diameter is supported, the above mandrels must be replaced with mandrels whose shape corresponds to the different opening diameter. As a result, to make silencers having various types of sections, pairs of mandrels as many as the number of the sections must be prepared and a setup process for the mandrels is required.
Accordingly, the cost of mandrels and a setup cost therefor are incurred in this arrangement, and the efficiency of the operation is lowered due to the time consumed by the setup.
An object of the present invention is to provide a shell lock seaming machine which has a shell case support mechanism capable of supporting shell cases having various types of sections without the need of setup to thereby increase productivity when many types of shell cases are made by mixture.